Design, Construction and Performance of ... - Geosystems, LP

Introduction
As documented by Weaver and Bruce (2007), grout curtains have been used in the
U.S. to control seepage in rock masses under and around dams of all types since the
1890’s. For a variety of understandable, if not always laudable reasons, the long-term
performance of many of these curtains has not been satisfactory, especially in lithologies
containing soluble and/or erodible materials. Foundation remediation in such instances
traditionally involved regrouting, often of course, using the same means, methods and
materials whose defects were the underlying cause of the inadequacy in the first place.
Disillusionment on the part of owners and engineers with the apparent inability of
these traditional grouting practices to provide a product of acceptable efficiency and
durability led to the chorus of “grouting doesn’t work” voices in the industry from the
mid-1970’s onwards. The fact that effective and durable grout curtains were being
installed successfully elsewhere in the world, using different perspectives on design,
construction and contractor procurement processes, largely escaped the attention of the
doubters who, for all their other and obvious qualities, exhibited technological
xenophobia.
Partly as a result of the anti-grouting lobby, equally in response to indisputable
geological realities and challenges and building on technical advances in “slurry wall”
techniques, the concept and reality of “positive cut-offs” became the mantra for major
embankment dam foundation rehabilitation in North America from 1975 onwards. Such
walls, built through and under existing dams by either the panel wall technique, or secant
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